In the cleaning of walls such as a container wall, it is necessary to use a liquid jet which impinges on the wall with a comparatively high jet force. All parts of the wall must be reached with the jet in order to achieve the desired cleaning effect. In the case of, for example, a cylindrical container, it is advantageous to use a rotating nozzle head which itself sprays the jet over the entire inner circumferential surface of the container. The cleaning fluid that flows through the nozzle is used to rotate the nozzle head.
To be effective, a rotating nozzle head must run slowly in order to insure thorough cleaning of the container wall rather than mere wetting of the wall. High speed nozzles produce a spray jet of fine particles which are retarded by ambient atmosphere and do not impinge on the container wall with sufficient velocity to ensure effective cleaning of the wall. Moreover, it is desirable that the nozzle head rotate at a speed that is substantially independent of the pressure of the cleaning fluid and especially when the cleaning fluid is foam. In order to provide a slowly rotating nozzle head, it is a known practice to use the cleaning fluid to drive a turbine which acts through a gear to rotate the nozzle head. The requirement for a gear makes the nozzle structure relatively expensive.